Obstacle Traversing Wheel Assembly

ABSTRACT

An obstacle traversing wheel assembly can include at least one primary wheel member mounted with a primary axis of rotation and capable of rolling engagement with a supporting surface, and at least one secondary wheel member mounted with a secondary axis of rotation. The secondary wheel member can have a plurality of surface engaging protrusions which enable the wheel assembly to traverse an obstacle by imparting climbing movement to the primary wheel member in response to engagement with the obstacle. The surface engaging protrusions can be defined by rolling wheel members. The obstacle traversing wheel assembly can be incorporated on a wide variety of wheel-bearing devices, such as wheelchairs, personal transportation devices, and intravenous fluid support racks.

FIELD OF THE INVENTION

The invention relates to a land vehicle having a running gear supporting a load carrier to adapt the vehicle to move over a surface for ascending or descending steps or similar obstructions, and more particularly to obstacle traversing wheel assemblies and vehicles associated therewith.

BACKGROUND

Known wheel-bearing devices are best for use on level surfaces. These known wheel-bearing devices suffer from various disadvantages including the requirement that traversing obstacles or bumpy terrain with a known wheel assembly requires more force or torque than when travelling across substantially smooth surfaces. The obstacle traversing problem associated with conventional wheels has been previously addressed by adding an additional centered climbing wheel and in another solution, adding deployable protrusions to the wheel. These configurations suffer the disadvantage of requiring a user to identify an obstacle before actually implementing the obstacle traversing device. For examples of various configurations of known wheel assemblies, see the devices disclosed in U.S. Pat. No. 795,620; U.S. Pat. No. 1,326,679; U.S. Pat. No. 2,736,564; U.S. Pat. No. 4,247,125; U.S. Pat. No. 5,427,398; U.S. Pat. No. 7,980,335; U.S. Pat. No. 8,240,407; U.S. Published Application No. 2005/0087940A1; U.S. Published Application No. 2005/0263965A1; U.S. Published Application No. 2007/0222165A1; U.S. Published Application No. 2009/0309319A1; U.S. Published Application No. 2011/0127732A1; European Published Application No. EP 13 23 401; and International Published Application No. WO 2002/12002. While each of these devices appears suitable for its intended purpose, the configurations disclosed are generally complex and costly to manufacture, while being less than satisfactory in operation. The problem with centered climbing wheel attachments, for example, is that the configuration creates an unstable condition for occupants of a wheel chair with only three points of contact increasing the likelihood of tipping the occupant out of the wheel chair when traversing a curb or other obstacle. Other configurations provide only limited ability to climb obstacles of varying vertical height. It would be desirable to provide an obstacle traversing wheel assembly with a simple construction. It would be desirable to provide an obstacle traversing wheel assembly with lower manufacturing costs. It would be desirable to provide an obstacle traversing wheel assembly with a satisfactory stable operating condition, while being able to traverse obstacles of varying vertical height.

SUMMARY

An obstacle traversing wheel assembly can include at least one primary wheel member. Each primary wheel member can be mounted with respect to a primary axis of rotation. Each primary wheel member can be capable of rolling engagement with a supporting surface. At least one secondary wheel member can be mounted with respect to a secondary axis of rotation. At least five supporting-surface-engaging portions enable the obstacle traversing wheel assembly to traverse an obstacle by imparting climbing movement to the at least one primary wheel member in response to engagement with the obstacle. The at least five supporting-surface-engaging portions can be associated with one of the at least one primary wheel member and the at least one secondary wheel member.

An obstacle traversing wheel assembly can have a primary wheel member mounted to a primary axis of rotation. An outer periphery of the primary wheel member can be capable of rolling engagement with a supporting surface. The primary wheel member can be supported by an axial pin or shaft. At least one secondary wheel member can be mounted having a common axis of rotation with respect to the primary axis of rotation. The at least one secondary wheel member can be separate from the primary wheel member. Five supporting-surface-engaging portions can be located on the at least one secondary wheel member and can extend radially outwardly beyond the outer periphery of the primary wheel member for enabling the obstacle traversing wheel assembly to traverse an obstacle by imparting climbing movement to the primary wheel member in response to engagement of at least one of the five supporting-surface-engaging portions of the at least one secondary wheel member with the obstacle.

An obstacle traversing wheel assembly can include a primary wheel member mounted with respect to a primary axis of rotation. The primary wheel member can have an outer periphery capable of rolling engagement with a supporting surface. At least one secondary wheel member can be mounted adjacent to the primary wheel member and axially offset with respect to the primary wheel member along the primary axis of rotation to provide independent coaxial rotation of the primary wheel member and the at least one secondary wheel member with respect to one another. Five supporting-surface-engaging portions can be located on the at least one secondary wheel member and can extend radially outwardly beyond the outer periphery of the primary wheel member for enabling the obstacle traversing wheel assembly to traverse an obstacle by imparting climbing movement to the primary wheel member in response to engagement of at least one of the five supporting-surface-engaging portions of the at least one secondary wheel member with the obstacle.

An obstacle traversing wheel assembly can include a primary wheel member mounted with respect to a primary axis of rotation and two secondary wheel members mounted with respect to a secondary axis of rotation. Each of the two secondary wheel members can have five supporting-surface-engaging protrusions. The primary axis of rotation can be located coaxial with the secondary axis of rotation. The secondary wheel members can extend vertically on each side of the primary wheel member and the secondary wheel members can rotate independent of one another or can be conjoined with one another for rotation as a unitary member. The five supporting-surface-engaging protrusions can enable the wheel assembly to traverse an obstacle by imparting climbing movement to the primary wheel member in response to engagement with the obstacle. The supporting-surface-engaging protrusions can include a rolling wheel member associated with each protrusion, such that each rolling wheel member rotates about a corresponding third axis of rotation.

The obstacle traversing wheel assembly can include a configuration having five primary wheel members, where each of the five primary wheel members rotates about a corresponding primary axis of rotation. A secondary wheel member can be mounted with respect to a secondary axis of rotation and can have five supporting-surface-engaging protrusions. The secondary wheel member can support the five primary wheel members in equally angularly spaced locations and at radially equal distances from the secondary axis of rotation. The secondary wheel member can enable the wheel assembly to traverse the obstacle by imparting climbing movement to the primary wheel members in response to engagement with the obstacle.

The wheel assembly can include a configuration having a swivel joint connecting each primary wheel member with respect to the secondary wheel member. The swivel joint can be a castor assembled to the secondary wheel member at radially equal distances from the secondary axis of rotation and at equally angularly spaced locations about the secondary axis of rotation. Each swivel joint can include an axis of rotation extending generally perpendicular to and offset from the secondary axis of rotation. In other words, the swivel axis of rotation can extend generally tangential to an imaginary circumference radially spaced from the second axis of rotation.

The obstacle traversing wheel assembly can be incorporated into various load carrying land vehicles, by way of example and not limitation, such as wheelchairs, intravenous (IV) dispensing devices, personal transport devices, or any other wheel-bearing device which can require traversing obstacles. Other applications of the present invention will become apparent to those skilled in the art when the following description of one mode contemplated for practicing the invention is read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like parts throughout the several views, and wherein:

FIG. 1A is a side elevation view of an obstacle traversing wheel assembly having at least one primary wheel member and at least one secondary wheel member;

FIG. 1B is a side view of the wheel assembly shown in FIG. 1A;

FIG. 1C is a front view of the wheel assembly shown in FIG. 1A;

FIG. 1D is a cross sectional view of the wheel assembly of FIG. 1A taken as shown in FIG. 1B;

FIG. 2A is a side elevation view of the wheel assembly from FIG. 1A with rolling wheel members located adjacent an outer radial end of each supporting-surface-engaging protrusion of the secondary wheel member;

FIG. 2B is a side view of the wheel assembly shown in FIG. 2A;

FIG. 2C is a front view of the wheel assembly shown in FIG. 2A;

FIG. 2D is a cross sectional view of the wheel assembly of FIG. 2A taken as shown in FIG. 2B;

FIG. 3A is a side elevation view of the wheel assembly having five primary wheel members supported for rotation by at least one secondary wheel member;

FIG. 3B is a side view of the wheel assembly shown in FIG. 3A;

FIG. 3C is a front view of the wheel assembly shown in FIG. 3A;

FIG. 3D is a cross sectional view of the wheel assembly of FIG. 3A taken as shown in FIG. 3B;

FIG. 4A is a side elevation view of the wheel assembly shown in FIG. 3A having one secondary wheel member;

FIG. 4B is a side view of the wheel assembly shown in FIG. 4A;

FIG. 4C is a front view of the wheel assembly shown in FIG. 4A;

FIG. 4D is a cross sectional view of the wheel assembly of FIG. 4A taken as shown in FIG. 4B;

FIG. 5A is a side elevation view of the wheel assembly shown in FIG. 3A having swivel joint connectors;

FIG. 5B is a side view of the wheel assembly shown in FIG. 5A;

FIG. 5C is a front view of the wheel assembly shown in FIG. 5A;

FIG. 5D is a cross sectional view of the wheel assembly of FIG. 5A taken as shown in FIG. 5B;

FIG. 6 is a perspective view of the obstacle traversing wheel assembly in combination with a wheelchair;

FIG. 7 is a perspective view of the obstacle traversing wheel assembly in combination with wheel-bearing furniture; and

FIG. 8 is a perspective view of the obstacle traversing wheel assembly in combination with a wheel-bearing device or load carrying vehicle.

DETAILED DESCRIPTION

The following description is of one presently contemplated mode of carrying out the invention of an obstacle traversing wheel assembly, capable of incorporation in personal transportation devices, such as wheelchairs. The wheel assembly of the present invention is configured for travelling on substantially level surfaces, travelling on uneven surfaces, or climbing steps.

Referring now to FIGS. 1A-D, there is shown an obstacle traversing wheel assembly 10 having at least one primary wheel member 12 and at least one secondary wheel member 18. By way of example and not limitation, the illustrated configuration includes one primary wheel member 12 and one secondary wheel member 18. The secondary wheel member 18 can have two secondary wheel member portions 18 a, 18 b independently rotatable with respect to one another or connected to one another to rotate in unison as a single monolithic unitary member, independently of the primary wheel member 12. Primary wheel member 12 is capable of rolling on a supporting surface, such that an outer periphery 14 of primary wheel member 12 contacts and rolls along the supporting surface. As best seen in FIG. 1A, primary wheel member 12 can be interposed between two secondary wheel members 18 a and 18 b. Secondary wheel member 18 can have three or more protrusions 22. By way of example and not limitation, as illustrated each secondary wheel member 18 can include five protrusions 22 a, 22 b, 22 c, 22 d, 22 e. Protrusions 22 a-22 e can have supporting-surface-engaging portions 40 a, 40 b, 40 c, 40 d, 40 e extending along a portion of the outer periphery of each protrusion. Each supporting-surface-engaging portion 40 can make contact with an obstacle when in a lower forwardly facing position with respect to a direction of travel and after contacting the obstacle, can make contact with one or both the obstacle and supporting surface during operation of obstacle traversing wheel assembly 10. By way of example and not limitation, as illustrated five protrusions can optimize the size of the obstacle which can be traversed while providing more structural support for the obstacle traversing wheel assembly 10 during traversing movement over an obstacle. The secondary wheel member 18 depicted in FIGS. 1A-C allows contact and/or sliding movement of the secondary wheel member 18 with respect to an obstacle simplifying the construction of the wheel assembly. In this manner, the secondary wheel member 18 does not require rolling wheel members 26 as illustrated in FIGS. 2A-2D, which can make the wheel assembly more cost effective to produce. By way of example and not limitation, when the obstacle traversing wheel assembly 10 is configured to have five protrusions 22, each protrusion can be located at an angle of about 72 degrees from adjacent protrusions in equally angularly spaced locations with respect to the secondary axis of rotation for the secondary wheel member 18.

It should be recognized by those skilled in the art that secondary wheel members 18 can be attachable to a pre-existing primary wheel member 12. In this case, the secondary wheel member 18 can be coupled to an existing support shaft, which can couple the wheel assembly to an existing bracket 36. By way of example and not limitation, as depicted in FIG. 1C, the axial pin or support shaft is sheathed within the sleeve portion 18 c of the secondary wheel member 18. The sleeve portion 18 c of the secondary wheel member 18 can allow for free rotation of secondary wheel member 18 independently of the primary wheel member 12 and can reduce friction between the parts during movement relative to one another. As best seen in FIG. 1C, a first bearing surface 32 can be located between primary wheel member 12 and the sleeve portion 18 c of the secondary wheel member 18. A second bearing surface 34 can be located between the secondary wheel member 18 and the support shaft 44. The assembly 10 including secondary wheel member 18 (defined by secondary wheel member portions 18 a, 18 b and sleeve portion 18 c), primary wheel member 12, and the support shaft 44 can be attached to a bracket 36 via a fastener 42. Bracket 36 can be affixed to a wheel bearing device, or load carrying vehicle, by way of example and not limitation, such as a wheelchair, via a swivel attachment post or bracket support shaft 38.

Primary wheel member 12 can rotate about a primary shaft 16 defining a primary axis of rotation and secondary wheel member 18 can rotate about a secondary shaft 20 defining secondary axis of rotation. The primary wheel member 12 can rotate about an axis of rotation parallel to an axis of rotation of the secondary wheel member 18. By way of example and not limitation, as illustrated in FIGS. 1A-1D, the primary shaft 16 defining the primary axis of rotation can be located coaxial with the secondary axis of rotation defined by the secondary shaft 20. In other words, as illustrated in FIGS. 1A-1D, the primary shaft 16 and secondary shaft 20 can be the same common shaft defining a coaxial common axis of rotation for the primary wheel member 12 and secondary wheel member 18. Secondary wheel member 18 can rotate uniformly and independently from primary wheel member 12. As best seen in FIG. 1B, an outer periphery 14 of the primary wheel member 12 can be located at a radial distance from primary axis of rotation of primary shaft 16. Protrusions 22 a-22 e can extend radially outwardly beyond the outer periphery 14 of the primary wheel member 12. Secondary wheel members 18 can rotate when the primary wheel member 12 rolls one of the outwardly extending protrusions 22 a-22 e into contact with an obstacle. The secondary wheel member 18 begins to rotate about the secondary axis of rotation in response to contact with the obstacle and continued movement of the wheel assembly toward the obstacle, thereby imparting a vertical climbing motion or catapulting action to the primary wheel member 12 enabling the obstacle traversing wheel assembly 10 to traverse the obstacle.

The term “obstacle” as used herein is defined as any physical structure which has a vertical height elevated from the height of a substantially level surface on which the wheel-bearing device or load carrying vehicle travels. Obstacles can include, but are not limited to, rocks, ridges, bumps, curbs, or other physical obstructions which can not be traversed by the normal rolling motion of the primary wheel member without some type of additional assistance to elevate the primary wheel vertically. The wheel assembly can be configured to not only traverse obstacles, but also to climb steps of elevated heights. Protrusions 22 a-22 e can be located on secondary wheel member portions 18 a and 18 b to catapult the obstacle traversing wheel assembly 10 in a vertical direction in response to engagement with the obstacle.

While traveling on a substantially level surface, the secondary wheel member 18 can be located in an angular position with respect to the primary wheel member 12, such that protrusions 22 extend outwardly without engaging the supporting surface 46 on which the primary wheel is in rolling contact. After contact with an obstacle having a higher vertical height than the supporting surface 46, one of the supporting-surface-engaging portions 40 a-40 e located on a corresponding one of the protrusions 22 a-22 e can act as a lever about which the obstacle traversing wheel assembly 10 rotates over the obstacle. Protrusions 22 a-22 e minimize the force and torque required to traverse an obstacle. After traversing the obstacle, the supporting-surface-engaging portions 40 a-40 e can return to a neutral or non-engagement orientation or position, where the protrusion 40 a-40 e can extend outwardly without engaging the supporting surface 46 as the wheel assembly travels along the substantially level surface with the primary wheel member 12 in rolling contact with the supporting surface 46.

Referring now to FIGS. 2A-2D, an obstacle traversing wheel assembly 10 can include protrusions 22 a-22 e with a plurality of rolling wheel members 26 a, 26 b, 26 c, 26 d, and 26 e. One rolling wheel member 26 a-26 e can be supported adjacent to a radially outwardly extending end of each corresponding protrusion 22 a-22 e for rotation about a corresponding third shaft 24 defining a third axis of rotation extending parallel to and radially spaced from the primary shaft 16 defining the primary axis of rotation and the secondary shaft 20 defining the secondary axis of rotation. As illustrated in FIGS. 2A-2D, the rolling wheel members 26 a-26 e can rotate about corresponding third shafts 24 a-24 e defining third axes of rotation. Rolling wheel members 26 a-26 e can catapult the obstacle traversing wheel assembly 10 in a vertical direction in response to engagement with the obstacle as previously described with respect to the protrusions 22 a-22 e. In this case the rolling wheel members 26 a-26 e allow rolling contact with the obstacle rather than the sliding or stationary contact of the supporting-surface-engaging portions (or more accurately obstacle-surface-engaging portions) 40 a-40 e.

Referring now to FIGS. 3A-3D, an obstacle traversing wheel assembly 10 can include a plurality of primary wheel members 12 a, 12 b, 12 c, 12 d, 12 e capable of rolling engagement with a supporting surface 46. The secondary wheel member can provide a rotational climbing function. The size of the primary wheels are indirectly proportional to the distance between the contact points of the traversing wheel assembly, hence, smaller primary wheels provide greater distance between the contact points of the obstacle traversing wheel assembly and the obstacle. A greater distance between contact points of the traversing wheel assembly allows the secondary wheel to have a greater turning radius. By way of example and not limitation, one configuration of an obstacle traversing assembly can include the primary wheel members can having a 2 inch diameter dimension to be mounted on an 8 inch diameter dimension for the secondary wheel member of the obstacle traversing wheel assembly. Primary wheel members 12 a-12 e can each rotate about primary shafts 16 a, 16 b, 16 c, 16 d, 16 e defining separate individual primary axes of rotation. As shown in FIGS. 3A-C, secondary wheel member 18 can include first and second portions 18 a, 18 b for supporting the primary wheel members 12 a-12 e in equal angularly spaced locations and at radially equal distances from a secondary wheel support shaft 20 defining a secondary axis of rotation. Primary wheel support shafts 16 a-16 e defining separate individual axes of rotation and can be located parallel to and offset from the secondary wheel member support shaft 20 defining the secondary axis of rotation. Primary wheel members 12 a-12 e can catapult the obstacle traversing wheel assembly 10 in a vertical direction in response to engagement with an obstacle. The obstacle traversing wheel assembly 10 can provide a secondary wheel member having at least one portion 18 a, 18 b located on either side of the primary wheel members 12 a-12 e to reduce any twisting or pivoting movement of primary wheel members 12 a-12 e which could cause the wheel-bearing device or load carrying vehicle to lose alignment with the direction of travel, potentially tipping the wheel-bearing device or load carrying vehicle.

Referring now to FIGS. 4A-4D an obstacle traversing wheel assembly 10 can include a plurality of primary wheel members 12 a-12 e and a secondary wheel member 18 having one portion 18 a located on one side of the primary wheel members 12 a-12 e. The secondary wheel member 18 can support the primary wheel members 12 a-12 e from a single side in a cantilevered fashion with the primary shafts 16 a-16 e. By way of example and not limitation, the illustrated configuration includes a robust secondary wheel member 18 a and can include stiffening ribs or webs as required to achieve the desired rigidity of the part.

Referring now to FIGS. 5A-5D, an obstacle traversing wheel assembly 10 can include a plurality of primary wheel members 12 a-12 e connected to a secondary wheel member 18 via separate individual swivel joint 28 a-28 e. The secondary wheel member 18 can include protrusions 22 a-22 e. One of the plurality of primary wheel members 12 a-12 e can be connected to each corresponding protrusion 22 a-22 e via a separate individual swivel joint 28 a, 28 b, 28 c, 28 d, 28 e. The swivel joints 28 a-28 e permit each corresponding primary wheel members 12 a-12 e to rotate on a corresponding swivel axes of rotation 30 a, 30 b, 30 c, 30 d, and 30 e. The swivel axes of rotation 30 a-30 e can be located in equally angularly spaced locations and at radially equal distances from the secondary shaft 20 defining the secondary axis of rotation. The swivel axes of rotation 30 a-30 e can be perpendicular to and offset from each corresponding primary shaft defining the corresponding primary axes of rotation 16 a-16 e. By way of example and not limitation, the swivel joint 28 can be defined by a castor. The wheel assembly 10 of FIGS. 5A-5D provides an additional degree of freedom as a result of the swivel joints 28 a-28 e. This allows the wheel-bearing device or load carrying vehicle to travel in a different direction while traversing the obstacle rather than being limited to traveling linearly during traversal of the obstacle.

Referring now to FIG. 6, the obstacle traversing wheel assembly 10 can be used in combination with a wheel chair device. In this configuration, the wheel chair is capable of ascending or descending stairs, curbs, or other vertically extending obstacles that would normally impair travel of a conventional wheel across a non-planar supporting surface. It should be recognized that any of the disclosed wheel assembly configurations can be used in combination with a wheel chair to permit traverse over vertically extending obstacles of varying height. In this manner, a stable operating configuration having at least four points of contact is provided while climbing an obstacle to minimize the likelihood of tipping an occupant out of the wheel chair. The wheel assembly can have a simple structure in order to be manufactured at a lower cost than compared to other alternative devices.

It should be recognized that the secondary wheel members of FIGS. 1A-1D or 2A-2D can be manufactured as an add-on assembly for existing wheel structures. The add-on kit can include the secondary wheel members and fasteners for attachment to an existing support pin or shaft of the existing wheel structure. In this manner, the secondary wheel members can be attached to the existing support pin or shaft of the existing wheel assembly for rotation in response to contact with an obstacle to obtain the desired climbing action over an obstacle. As previously described, the outer peripheral surface of the secondary wheel member, as best seen in FIGS. 1A-1D, or the rolling members attached thereto, best seen in FIGS. 2A-2D extend beyond the outer periphery or circumference of the primary wheel member to allow catapulting action in response to contact with a vertically extending obstacle.

In operation, the wheel assembly uses the primary wheel member to roll along the supporting surface until contact is made with an obstacle. In the configuration of FIG. 1A-1D, the secondary wheel member can contact the obstacle and begin to rotation. Rotation of the secondary wheel member catapults the primary wheel vertically with respect to the obstacle. If the obstacle is vertically higher, another protrusion of the secondary wheel member can contact the obstacle to catapult the primary wheel vertically higher. After the summit of the obstacle is obtained by the climbing action of the secondary wheel member, the primary wheel can contact the supporting surface and roll in a normal fashion. When traversing generally flat planar surfaces, the primary wheel supports the assembly and the second wheel member is in a position as shown in FIG. 1B not contact the supporting surface.

Similarly, with respect to FIGS. 2A-2D, the wheel assembly uses the primary wheel member to roll along the supporting surface until contact is made with an obstacle. The secondary wheel member can then contact the obstacle with a rolling member and the secondary wheel member can begin to rotation as the rolling member rotates along the obstacle. Rotation of the secondary wheel member catapults the primary wheel vertically with respect to the obstacle. If the obstacle is vertically higher, another protrusion of the secondary wheel member can contact the obstacle with another rolling member to further catapult the primary wheel vertically higher. After the summit of the obstacle is obtained by the climbing action of the secondary wheel member, the primary wheel can contact the supporting surface and roll in a normal fashion. When traversing generally flat planar surfaces, the primary wheel supports the assembly and the second wheel member is in a position as shown in FIG. 2B not in contact with the supporting surface.

Referring again to FIGS. 3A-3D and 4A-4D, in operation the wheel assembly uses the primary wheel member to roll along the supporting surface until contact is made with an obstacle. After one of the primary wheel members contacts the obstacle, then the secondary wheel member can begin to rotate, as the primary wheel member rotates along the obstacle. Rotation of the secondary wheel member catapults the other primary wheel members vertically with respect to the obstacle. If the obstacle is vertically higher, another protrusion of the secondary wheel member can rotationally present another primary wheel member for contact with the obstacle to further catapult the primary wheel vertically higher. After the summit of the obstacle is obtained by the climbing action of the secondary wheel member, the primary wheel members can contact the supporting surface and roll in a normal fashion. When traversing generally flat planar surfaces, the primary wheel members support the assembly and the second wheel member as shown in FIGS. 3B and 4B.

Referring now to FIGS. 5A-5D, in operation the wheel assembly uses the primary wheel member to roll along the supporting surface until contact is made with an obstacle. After one of the primary wheel members contacts the obstacle, then the secondary wheel member can begin to rotation, as the primary wheel member rotates along the obstacle. Rotation of the secondary wheel member catapults the other primary wheel members vertically with respect to the obstacle. If the obstacle is vertically higher, another protrusion of the secondary wheel member can rotationally present another primary wheel member for contact with the obstacle to further catapult the primary wheel vertically higher. After the summit of the obstacle is obtained by the climbing action of the secondary wheel member, the primary wheel members can contact the supporting surface and roll in a normal fashion. When traversing generally flat planar surfaces, the primary wheel members support the assembly and the second wheel member as shown in FIG. 5B.

Referring now to FIG. 7, the obstacle traversing wheel assembly 10 can be used in combination with wheel-bearing furniture. In this configuration, the wheel bearing furniture is capable of ascending or descending cords, mats, or other vertically extending obstacles that would normally impair travel of a conventional wheel across a non-planar supporting surface. It should be recognized that any of the disclosed wheel assembly configurations can be used in combination with wheel-bearing furniture to permit traverse over vertically extending obstacles of varying height.

Referring now to FIG. 8, the obstacle traversing wheel assembly 10 can be used in combination with another wheel-bearing device or load carrying vehicle. In this configuration, the load carrying vehicle is capable of ascending or descending stairs, curbs, or other vertically extending obstacles that would normally impair travel of a conventional wheel across a non-planar supporting surface. It should be recognized that any of the disclosed wheel assembly configurations can be used in combination with a load carrying vehicle to permit traverse over vertically extending obstacles of varying height.

While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law. 

What is claimed is:
 1. An obstacle traversing wheel assembly comprising: at least one primary wheel member, each primary wheel member mounted with respect to a primary axis of rotation, each primary wheel member capable of rolling engagement with a supporting surface; at least one secondary wheel member mounted with respect to a secondary axis of rotation; and at least five supporting-surface-engaging portions for enabling the obstacle traversing wheel assembly to traverse an obstacle by imparting climbing movement to the at least one primary wheel member in response to engagement with the obstacle, the at least five supporting-surface-engaging portions associated with one of the at least one primary wheel member and the at least one secondary wheel member.
 2. The obstacle traversing wheel assembly of claim 1, wherein the at least one primary wheel member of the obstacle traversing wheel assembly further comprises at least five primary wheel members defining the at least five supporting-surface-engaging portions.
 3. The obstacle traversing wheel assembly of claim 2, wherein the at least one secondary wheel member supports the at least five primary wheel members in equally angularly spaced locations and radially equal distances from the secondary axis of rotation, wherein each primary axis of rotation is parallel to and offset from the secondary axis of rotation.
 4. The obstacle traversing wheel assembly of claim 2 further comprising: a plurality of swivel joints, each swivel joint connecting one of the at least five primary wheel members with respect to the at least one secondary wheel member, each swivel joint having a swivel axis of rotation perpendicular to and offset from a corresponding primary axis of rotation of a corresponding connected primary wheel member, the plurality of swivel joints located in equally angularly spaced locations and radially equal distances from the secondary axis of rotation, wherein each swivel joint permits the corresponding connected primary wheel member to rotate on the corresponding swivel axis of rotation.
 5. The obstacle traversing wheel assembly of claim 4, wherein the swivel joint is a castor.
 6. The obstacle traversing wheel assembly of claim 1, wherein the primary axis of rotation is coaxial with the secondary axis of rotation to define a common axis of rotation and the at least five supporting-surface-engaging portions are located on the at least one secondary wheel member.
 7. The obstacle traversing wheel assembly of claim 6, wherein the at least one primary wheel member rotates independently of the at least one secondary wheel member, such that the at least five supporting-surface-engaging portions of the at least one secondary wheel member catapults the obstacle traversing wheel assembly in a vertical direction in response to engagement with the obstacle.
 8. The obstacle traversing wheel assembly of claim 7, wherein each of the at least five supporting-surface-engaging portions include a rolling wheel member, each rolling wheel member having a third axis of rotation parallel to and radially spaced from the primary and secondary axes of rotation.
 9. The obstacle traversing wheel assembly of claim 7, wherein the at least one primary wheel member further comprises a single primary wheel member and the at least one secondary wheel member further comprises a first secondary wheel member, and the first secondary wheel member is mounted adjacent to the single primary wheel member, such that the primary wheel member and secondary wheel member are rotatable parallel to one another and offset from one another along the common axis of rotation.
 10. The obstacle traversing wheel assembly of claim 7, wherein the at least one primary wheel member further comprises a single primary wheel member and the at least one secondary wheel member further comprises first and second secondary wheel members, and the first and second secondary wheel members are mounted adjacent to each side of the single primary wheel member, such that the single primary wheel member is interposed between the first and second secondary wheel members allowing the primary wheel member and secondary wheel members to rotate parallel to one another while being offset from one another along the common axis of rotation, and the first and second secondary wheel members rotatable independently of one another, and independently of the single primary wheel member.
 11. The obstacle traversing wheel assembly of claim 7 further comprising: an outer periphery of the at least one primary wheel member located at a radial distance from the primary axis; and the supporting-surface-engaging portions of the at least one secondary wheel member extending beyond the outer periphery of the at least one primary wheel member.
 12. The obstacle traversing wheel assembly of claim 7, wherein the at least one secondary wheel member rotates when the at least one primary wheel member encounters the obstacle, such that the at least one secondary wheel member imparts vertical climbing motion to the at least one primary wheel member in response to engagement of the at least one secondary wheel member with the obstacle.
 13. In an obstacle traversing wheel assembly having a primary wheel member mounted to a primary axis of rotation, an outer periphery of the primary wheel member capable of rolling engagement with a supporting surface, the primary wheel member supported by an axial pin, the improvement comprising: at least one secondary wheel member mounted having a common axis of rotation with respect to the primary axis of rotation, the at least one secondary wheel member separate from the primary wheel member; and five supporting-surface-engaging portions located on the at least one secondary wheel member and extending radially outwardly beyond the outer periphery of the primary wheel member for enabling the obstacle traversing wheel assembly to traverse an obstacle by imparting climbing movement to the primary wheel member in response to engagement of at least one of the five supporting-surface-engaging portions of the at least one secondary wheel member with the obstacle.
 14. The improvement of claim 13, wherein the at least one secondary wheel member is attachable to the obstacle traversing wheel assembly by the axial pin.
 15. The improvement of claim 14, wherein the primary wheel member rotates independently of the at least one secondary wheel member, such that at least one of the five supporting-surface-engaging portions of the at least one secondary wheel member catapult the obstacle traversing wheel assembly in a vertical direction in response to engagement with the obstacle.
 16. The improvement of claim 13, wherein each of the five supporting-surface-engaging portions include a rolling wheel member, each rolling wheel member having a third axis of rotation parallel to and radially spaced from the primary and secondary axes of rotation, wherein the primary wheel member rotates independently of the at least one secondary wheel member, such that the rolling wheel member of at least one of the five supporting-surface-engaging portions of the at least one secondary wheel member catapults the obstacle traversing wheel assembly in a vertical direction in response to engagement with the obstacle.
 17. The improvement of claim 13, wherein the at least one secondary wheel member further comprises a first secondary wheel member, and the first secondary wheel member is mounted adjacent to the primary wheel member, such that the primary wheel member and the first secondary wheel member are rotatable parallel to one another and offset from one another along the common axis of rotation.
 18. The improvement of claim 13, wherein the at least one secondary wheel member further comprises first and second secondary wheel members, and the first and second secondary wheel members are mounted adjacent to each side of the primary wheel member, such that the primary wheel member is interposed between the first and second secondary wheel members allowing the primary wheel member and the first and second secondary wheel members to rotate parallel to one another while being offset from one another along the common axis of rotation, and the first and second secondary wheel members rotatable independently with respect to one another and independently of the primary wheel member.
 19. The improvement of claim 13 further comprising: the outer periphery of the primary wheel member located at a radial distance from the primary axis of rotation; and the supporting-surface-engaging portions of the at least one secondary wheel member extending beyond the outer periphery of the primary wheel member.
 20. An obstacle traversing wheel assembly comprising: a primary wheel member mounted with respect to a primary axis of rotation, the primary wheel member having an outer periphery capable of rolling engagement with a supporting surface; at least one secondary wheel member mounted adjacent to the primary wheel member and axially offset with respect to the primary wheel member along the primary axis of rotation to provide independent coaxial rotation of the primary wheel member and the at least one secondary wheel member with respect to one another; and five supporting-surface-engaging portions located on the at least one secondary wheel member and extending radially outwardly beyond the outer periphery of the primary wheel member for enabling the obstacle traversing wheel assembly to traverse an obstacle by imparting climbing movement to the primary wheel member in response to engagement of at least one of the five supporting-surface-engaging portions of the at least one secondary wheel member with the obstacle. 